Government agencies like USPS are not set up to be profitable. We The People have decided we want the Federal Government to handle our mail which, in the past was the main means of communication between individual citizens. We felt it was OK to spend tax revenue on the post.
Today, communication between people is via the Web, email, cell phones, etc. You don't need a mailman (mailperson) to deliver a letter to you. It seems that today, the USPS is mainly for packages and junk mail advertising. Hopefully Doge will get around to cutting the waste in the USPS.